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From: Andi Drebes <lists-receive@programmierforen.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Jörn Engel" <joern@logfs.org>,
	linux-fsdevel@vger.kernel.org, "Karel Zak" <kzak@redhat.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Phillip Lougher" <phillip@lougher.demon.co.uk>
Subject: Re: [PATCH 1/2] Make cramfs little endian only
Date: Tue, 4 Dec 2007 22:31:54 +0100	[thread overview]
Message-ID: <200712042231.54640.lists-receive@programmierforen.de> (raw)
In-Reply-To: <alpine.LFD.0.9999.0712041250280.32379@woody.linux-foundation.org>

> > Sure. This saves some definitions (and lines of code)...
> > Here's the new patch (tested on the same machines mentioned in the first message).
> > I tried to move as many lines as possible out of the endian dependent section.
> 
> This really is the totally wrong way to do this.
> 
> You should *not* convert inodes to CPU-endian mode at all. You should 
> *keep* them in the native mode, and then just use "le32_to_cpu()" when 
> actually using them.
OK. I'll prepare a new patch and send it to the list (not today,
it's already too late in the evening here). 

> Basically, if you ever have a
> 
> 	#ifdef __BIG_ENDIAN
> 
> or similar in the source code, you're simply doing something wrong. 
Perhaps I'm missing somehting, but I think for cramfs, unfortunately,
there has to be this statement. The bitfields in the cramfs_inode structure
cause some problems. You can't simply call le32_to_cpu() on them.
Especially the namelength and offset fields are weird. There has to be at least
one routine for each kind of machine that converts those values (or not -- depending
ont the machine's endianness).

> Btw, sparse can be a big help for things like this, by just marking the 
> actual disk data structures as being the right type (ie "__le32" and 
> friends), and then you can verify that any users will use "le32_to_cpu()" 
> as required, because sparse will warn about bad endianness.
Ok, thanks for your advice. But what about the problems mentioned above?

	Andi

  reply	other threads:[~2007-12-04 21:32 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-12-04 11:59 [PATCH 0/2] Make cramfs little endian only Andi Drebes
2007-12-04 12:01 ` [PATCH 1/2] " Andi Drebes
2007-12-04 15:34   ` Jörn Engel
2007-12-04 20:37     ` Andi Drebes
2007-12-04 20:58       ` Linus Torvalds
2007-12-04 21:31         ` Andi Drebes [this message]
2007-12-04 22:35           ` Linus Torvalds
2007-12-04 22:58             ` Jeff Garzik
2007-12-05 21:57               ` Andi Drebes
2007-12-05 22:21                 ` Linus Torvalds
2007-12-05 22:41                   ` Jörn Engel
2007-12-06 16:38                     ` Andi Drebes
2007-12-06 16:27                   ` Andi Drebes
2007-12-06 16:47                     ` Jörn Engel
2007-12-06 17:35                       ` Linus Torvalds
2007-12-06 17:31                     ` Linus Torvalds
2007-12-06 22:37                       ` Andi Drebes
2007-12-04 20:11   ` Andrew Morton
2007-12-04 20:58     ` Andi Drebes
2007-12-04 12:02 ` [PATCH 2/2] Update documentation Andi Drebes

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